Controlling and exhibiting apparatus



P 6, 1958 w. c. VIRBILA 2,852,197

CONTROLLING AND EXHIBITING APPARATUS Filed Dec. 51, 1953 4 Sheets-Sheetl Sept. 16, 1958 w. c. VlRBlLA 2,852,197

CONTROLLING AND EXHIBITING APPARATUS Filed Dec. 31, 1953 4 Sheets-Sheet2 F 1 7 200 K 1 44 PRESSURE TRANSMITTER I 110 I a; 46 M 51 GYM-1% J J]46' J44 jfliw 1 .3] z/E/Jj J6 PRESSURE fad 6/53 44/ REGULATOF 97 99/ Jg1 I; w

----|0 l5-- IO 15 lo l5- w- 'fl- 8( J m-ij 12K a; |2- j 07 e 6 L 6,? -ei o 3- O 3- -O 3 AUTO MAN AUTO MAN AUTO MAN AUTO MAN AUTO SEAL SEAL SEALSEAL SEAL Sept. 16, 1958 w. c. VIRBILA 2,852,197

' CONTROLLING AND EXHIBITING APPARATUS Filed Dec. 31, 1953 4Sheets-Sheet 5 Sept. 16, 1958 w. c. VlRBlLA CONTROLLING AND EXHIBITINGAPPARATUS 4 Sheets-Sheet 4 Filed Dec. 31, 1953 United States PatentC)CONTROLLING AND EXHIBITING APPARATUS William C. Virbila, Watertowu,Conn., assignor to The Bristol Company, Waterbury, Conn., a corporationof Connecticut Application December 31, 1953, Serial No. 401,634

14 Claims. (Cl. 236-82) The complexity of control functions in manymodern industrial processes, as, for example, oil refining, has led toan accumulation of controlling and recording instruments; and attemptsto centralize these in a common location have tended toward large andcumbersome panels, occupying a prohibitive amount of valuable space, andlikely to prove confusing to operators. Such considerations have led toa policy of miniaturization, involving a decrease in the size-especiallyin the panel areaof instruments, and also provision for maximumflexibility and interchangeability, making it possible to installindicators, recorders or controllers (or units combining any or all ofthese functions), as required, and, with a minimum of manipulation oradjustment, to remove one or more such instruments for replacement by aperfect instrument of the same type in case of damage or by acorresponding instrument of another type, as might be dictated by achange in process or procedure.

Since, in many instances, the interacting elements necessary to aninstrument performing its allotted function cannot practicably bereduced below certain critical dimensions, and therefore the volume ofan instrument cannot always be decreased in correspondence with thedesired reduction in panel area, it follows that redesign forminiaturization will result in a tendency to increase the length of aninstrument in a sense measured perpendicular to the face of the mountingpanel, so that the trend of design is toward a long and relativelyslender instrument, having a substantially square panel projection and adepth of the order of double the panel width or height.

It will be apparent that with a device of such proportions little in theway of servicing or adjustment can be done while the instrument is inplace on the panel, necessitating its withdrawal for even such routinematters as inking the pen or changing the chart. It will further beapparent that such withdrawal and all mani ulations involved in securingthe instrument in place or releasing it for removal must be effectedfrom the front. Otherwise, work on one instrument might require removalof one or more adjacent units to permit of necessary access to theelements.

It is an object of thepresent invention toprovide an instrument,alternatively of theindicating, recording or controlling form, or of acombinationof two or more of the above functions, adapted for removableand interchangeable installation in a standard panel mounting.

It is a further object to provide an instrument of the above naturewhich shall be adapted to non-interfering installation in immediateproximity to other, and sim-;

ilar, instruments and with a minimum of mechanical clearance therefrom.

It is a further object to provide an instrument of the above naturewhich may be securely and rigidly mounted in its operating location, andreadily removable therefrom with a minimum of interference with measuredor controlled functions or with the functioning of adjacent instruments.

It is a further object to provide an instrument of the above naturewhich may be partially withdrawn from its normal operating position forroutine servicing and without in any way interfering with its normalfunctioning, and which may be further and completely Withdrawn, andremoved from the installation, without the need for manipulatingelectrical or piping connections.

It is a further object to provide an instrument of the above naturewherein the control function may readily be transferred from automaticto manual, or manual to automatic, without a bump due to suddentransition from one to another of pressures in the control system, andwithout the necessity for comparing or coordinating readings ondifferent gauges.

The type of automatic regulating system to which the instrumentembodying the principles of the invention is especially applicable isthe pneumatic control of the force-balance class, embodying four units:(1) a pressure transmitter adapted to develop a fluid pressurerepresentative of the magnitude of a measured variable, (2) afluid-actuated control valve adapted to regulate the measured variablein accordance with the pressure of an actuating fluid applied thereto,(3) a pressure regulator adapted to receive pressure fluid from a sourceof supply, and to deliver fluid at an output pressure which may beadjusted at will by means of a mechanical device, (4)

of the encloslng case in which the instrument shown in a force-balancecontrol unit responsive to the difference between the pressures derivedfrom the transmitter and the pressure regulator and adapted thereby toregulate the fluid pressure applied to the control valve. Such aninstallation, as Well as its component elements, is fully set forth anddescribed in a paper The Solution of Instrumentation Problems by thePneumatic Null Balance Method by C. B. Moore, in the periodicalInstruments, vol. 18 (1945), page 598.

In the drawings:

Figure 1 is an isometric. representation of a recording instrumentembodying the principles of the invention.

Figure 2 is an isometric representation of a portion Figure 1 isnormally positioned for operation.

Figure 3 is a diagram of a pneumatic control system incorporating theprinciples of the'invention.

Figures 4 and 5 illustrate alternative positions'of certain elementsshown in Figure 3.

Figures 6, 7' and 8 illustrate the indicating scales of the instrument,respectively showing the several interrelated pointers or indexes inthree characteristic relative positions.

Figures 9, 10, 11, 12 and 13 illustrate positions of a manually actuatedmember of the apparatus corresponding respectively to different stagesin transition from one to another of several possible operatingpositions. ures 12 and 13 are duplicates respectively of Figures 10 and9, and are repeated in order to maintain a sequence of viewscorresponding to a sequence of events in manipulation of the apparatus.)

Figure 14 is a sectional view of certain mechanical elements of theapparatus embodying the principles of Figures 20, 21, 22 and 23 arebottom views to a slightly enlarged scale showing relative positions ofcertain coacting members corresponding to different positions of theremovable instrument assembly relative to its enclosing casing.

Referring now to the drawings, an indicating and recording instrumentassembly, generally designated as 31 in Figure 1, is adapted forremovable mounting in an enclosing case 32 normally forming a permanentpart of a panel member. As indicated by way of example, the instrument31 comprises an elongated sheet metal baseplate 33 having upon its uppersurface near one extremity (hereinafter to be known as the rear end),three mounting members 34, 35 and 36, carrying respectively threefluid-pressure-responsive elements 37, 38 and 39. While saidpressure-responsive elements are here shown as bellows members, it willbe apparent that they may take the form of Bourdon tubes or equivalentdevices whereby a fluid pressure may be caused to affect the position ofa mechanical element. Each of the mounting members 34, 35 and 36includes a portion projecting through the base plate 33 to its lowerside, as indicated in Figures 15, 16 and 17, and also contains aninternal passage, not shown in the drawings, whereby the interior of thecorresponding pressure element may be placed in communication withexterior conduit means hereinafter to be described.

A hearing pedestal 40 mounted upon the base-plate 33 carries a shaft orspindle member 41 upon which are freely pivoted three J-shaped levermembers 44, 45 and 46, each having a short arm and a long arm. The shortarms of the lever members 44, 45 and 46 are linked respectively to thepressure-responsive elements 37, 38 and 39, whereby deflection of any ofthe latter due to variations of internal fluid pressure will produce acorresponding angular displacement of the corresponding lever memberabout the spindle 41.

Carried by the base-plate 33 at the extremity thereof remote from themounting of the pressure-responsive elements (said extremity hereinafterto be known asthe front end) is indicating and recording meanscomprising a calibrated scale member and a juxtaposed strip chart member51. The scale member is vertically disposed and may carry two sets ofgraduations adapted to cooperate with index and pointer membershereinafter to be described in providing a plurality of indications ofmeasured variables. The graduations at the left side of the scale arepreferably calibrated in terms of the measured and regulated variable,and those at the right side of the scale in term of fluid pressureexisting in certain parts of the control system with which theinstrument assembly will be operatively associated. The general natureof the scale graduations will be understood from Figures 6, 7 and 8;and, as indicated in Figure 1, the right-hand edge of the scale mayexpediently be bent into a different plane from its front surface,rendering inconspicuous the usually less important control pressurereadings and facilitating uninhibited determination of the significantmagnitudes of the controlled variable.

The chart member 51 is disposed to lie in a vertical plane and is backedby a platen member 52, whereby to present a flat surface occupyingsubstantially three quarters of the front elevation of the instrument.The chart is supplied from a stock roll 53, passes around a guide member54 and a curved portion of the platen 52, between said platen and thescale 50'and around a drum 55 adapted for continuous rotation by meansof a timing motor or clock, not shown in the drawings. V

forations 56 near one edge, and adapted to be engaged by correspondinglyspaced pins 57 on the periphery of the drum 55, whereby to assurepositive driving. After leaving the driving drum 55 the chart iscollected on a re-.

The chart 3 paper 18 preferably provided with uniformly-spaced per- V 4ceiving roll 58, or other suitable receptacle, from which it may beremoved as required.

The long arm 44a of the lever member 44 extends from the rear to thefront end of the instrument, near one side thereof, passes between thescale 50 and the platen 52 and carries on its extremity a recording penor stylus 60, which bears upon the chart 51 near the right-hand edge ofthe platen. With changes in pressure values within the element 37, thelever member 44 will be correspondingly deflected, resulting in verticaldisplacement of the recording member 60, whereby there will be inscribedon the chart a graphic record of said pressure values. The long arm 44aof the lever member 44 carries also an index or pointer 61 movable withthe recording member 60, and providing upon the scale 50 an indicationof the pressure value as recorded upon the chart 51.

The long arm 45a of the lever 45 is extended in substantial parallelismto that of the lever 44 and in noninterfering relationship thereto, andterminates in an indicating member 62 cooperating, like the pointer 61,with the scale 50 to provide an indication of its deflected position,and hence of the pressure within the element 38. The indicating member62, while reading on the same scale as the pointer 61, movesindependently thereof, and may occupy any position with respect thereto,including a position of coincidence between the two. In order to avoidconfusion of reading, the member 62 (hereinafter, for reasons which willbecome apparent, referred to as the spotter) is made of a differentshape from the pointer 61, a preferred form being that in which it isprovided with flanking wings as indicated, so that it will at no time bewholly concealed by said pointer 61.

The long arm 46a of the lever member as is extended in a manner similarto those of the levers 44 and 45 and terminates in an index 63, passingpreferably on the side of the scale 50 remote from the pointer 61 andthe spotter 62, and so formed as to follow a path substantiallycoincident with that followed by said pointer and spotter, whereby itsdeflected position may be matched with that of either of the samewithout reference to actual scale readings. It will be understood thatany or all of the long arms of the lever members 44, 45 and 46 may bereplaced by straight-line motions, well known in the art and forming nopart of the present invention, whereby to eliminate the need forcurvature from the scale 5i) and from the surface of the chart 51.

For an understanding of the manner of supporting and securing theinstrument assembly 31 within the case 32, reference may be had toFigures 1 and 2 taken in conjunction with the sectional View of Figure14. To the opposed inner faces of the side walls of the case 32 aresecured parallel rail members '7 0 and 71, extending for a considerableportion of the length of the casing- The base-plate 33 of the instrumentassembly 31 is provided with turned-down edge portions 72 and 73 adaptedto engage said rails, whereby to support said assembly in longitudinallysliding relationship. Secured to the inner faces of the edge portions 72and 73 respectively, and preferably spaced inwardly therefrom, are anglestrips 74 and 75, disposed in a manner to project outward beneath therails and 71, forming longitudinal grooves or slots wherein said railsmay lie, and constraining the plate 33 and'parts carried thereby tolongitudinal displacement relative to the enclosing casing 32.

Formed in the rail 70 at a location near its front end is a gap or slot76, seen in Figure 2, and clearly shown in Figures 20-23, inclusive.engagement by a latch member 77 carried by the baseplate 33 and having adetent portion 78 adapted to enter said slot as the plate 33 attains apredetermined longitudinal displacement with respect to the'casing 32.The latch member 77 is pivotally mounted on the lower face of saidbase-plate, and by means of a spring member 79 1s urged for angulardisplacement in a clockwise sense as seen from the bottom of theassembly,'and as shown Said slot is positioned for.

in various figures of the drawings. Sajd latch member is provided with afinger piece 80 normally enclosed within the casing 32, but projectingthrough an opening in the edge portion 72 when the instrument assemblyis partially withdrawn, and thus accessible for manual operation of thelatch. Several possible positions of the latch member 77 in its coactionwith the slot 76 are shown in Figures 20, 21, 22 and23, and willhereinafter be more fully discussed.

The base-plate 33 is provided at its front end with a downwardlyprojecting lug 81 and the front portion of the case 32 carries athumb-screw 82 having a mutilated head, whereby as the instrument isinserted in the case the lug will pass over the screw, after which thelatter may be rotated through a portion of a turn, securing and clampingthe instrument assembly in its operating position. A manually operableknob 83 projecting through the lower portion of the front of the case 32is carried by a rotatable rod 84, whereby to actuate regulatinginstrumentalities presently to be described. A manually operableindicating handle 85 carried by a rotatable rod 86, whereby to establishthe position of a three-way valve also subsequently to be described,projects through the front of the case, may at will be set in any one ofthree positions designated Automatic, Seal and Manual, or by equivalentabbreviations.

Attention may now be directed to Figure 3, wherein is diagrammaticallyshown a pneumatic control system of the class with which the inventionis especially useful. The express purpose of the control installationused as an example is to measure the temperature of material within -acontainer or enclosure 90, as determined by a temperature-sensitiveelement 91 positioned therein, and on the basis of such measurement toregulate said temperature to a predetermined value by controlling theadmission of a temperature-affecting agent from a source 92 toheatexchange relation with said material. The control system embodiesfour more or less mutually distinct units as previously set forth in ageneral manner. These units may be recapitulated as (l) a pressuretransmitter 95, (2) a control valve 96, (3) a pressure regulator 97, and(4) a force-balance control unit 98.

The pressure transmitter 95 is a device adapted to develop a fluidpressure representative of the magnitude of a measured variable. In theform shown, the device 95 is provided with an inlet connected to asource of substantially constant air pressure 99, and with an outletconnected to a conduit 100, while connection to thetemperature-responsive element 91 is provided by means of a capillarytube 101. Transmitters of this class are well known in the art oftelemetering and automatic control, and may be of either theforce-balance or the position-balance type. The force-balance type ofpressure transmitter is described in the hereinbefore mentioned paper byMoore in Instruments, 1945. natively, the position-balance type oftransmitter is described in the book Principles and Methods ofTelemetering, by P. A. Borden and G. M. Thynell (Reinhold, 1948), page191. This device is also shown in British Patent No. 525,674 issuedNovember 21, 1940..

The control valve 96 is of a conventional form well known in the art,and here needs no description. It is provided with a body portionconnected to a conduit 102, whereby to regulate the flow ofheat-affecting agent therethrough from the source 92 to the container90. It is further provided with a fluid-pressure motor elementoperatively responsive to fluid pressure in a conduit 103 connectedthereto, whereby to close or open the passage through the body portionin accordance with the magnitude of said pressure.

The pressure regulator 97 and the control unit 98 are both described insaid paper by Moore. The regulator is connected to receive a supply ofair from the source 99 and to deliver it to a connected conduit 104, andat a constant pressure as established by adjustment effected Alter- 6 bythe knob 83 through the rod 84. The control unit 98 is adapted torespond to the difference between the pressures in the conduits 100 and104 connected thereto, and thereby to supply from the source 99 to aconnected outlet conduit an air pressure regulated in accordance withsaid pressure diiference.

A three-way valve 106, operable from the handle 85 through the rod 86,has connected thereto the conduits 103, 104 and 105 in such a mannerthat conduit 103 may at will be connected to either of the conduits 104and 105 or that all three of said conduits may be simultaneously sealed.The three positions of said valve are indicated in Figures 3, 4 and 5,respectively. While the apparatus of Figure 3, as thus far described,comprises a complete automatic control system, the manner of operativelyassociating the recording instrument 31 therewith will be briefly setforth before considering the performance of the controlling apparatus.

The conduits 100, 104i and 103 are individually and respectivelyconnected to self-sealing pneumatic receptacles 107, 108 and 109 in ablock 110 mounted in the rear portion of the enclosing case 32. Theinternal passages within the mounting members 34, 35 and 36 of theinstrument 31 are respectively connected to tubular plug members 114,and 116, carried by the base-plate 33 in a manner hereinafter to be setforth, and adapted to be removably inserted in the receptacles 107, 108and 109 whereby to provide separable connection of the respectiveconduits 100, 103 and 104 to the interiors of pressureresponsive bellowsmembers 37, 39 and 38. Thus, it will be seen that the pen 60 willprovide on the chart 51 a continuous record, and the pointer 61 on thescale 50 a continuous indication, of the pressure in the conduit 100,and therefore of the temperature to which the sensitive element 91 isexposed. Similarly, the spotter 62 will provide on the scale 50 acontinuous indication of the adjusted pressure in the conduit 104,against which the pressure in the conduit 100 is balanced in the controlunit 98. Likewise, the index 63 will provide an indication of thecontrol pressure existing in the conduit 103 and applied to the motorelement of the valve 96.

As previously stated, the scale 50 is provided with two sets ofgraduations, those at the left, as seen in the drawings, being common tothe pointer 61 and the spotter 62, and those at the right cooperatingwith the index 63 to provide an indication of its deflected position. Itwill be further observed that the index 63 extends across its allottedgraduations so that its tip follows a path substantially coincident withthose of said pointer and spotter, thus facilitating comparison of thephysical position of said index with that of either of said last namedelements. The graduations on the left-handside of the scale are in termsof the controlled variable-in the present instance, temperaturewhilethose on the right-hand edge are in units of pressure applied to themotor element of the valve 96.

Attention may now be directed to the performance of the control systemunder normal operating conditions. With the three-way valve set to theAutomatic position, as shown in Figure 3, and as indicated by themanually operable handle 85, the conduit 105 will be placed in directcommunication with the conduit 103, so that the output pressure of thecontrol unit 98 will be applied to the motor element of the valve 96.The pressure in the conduit 104, as adjusted by the regulator 97according to its manual setting by means of the knob 83, and asindicated bythe spotter 62 on the scale 50, will be impressed upon oneside of the differentially responsive element forming a part of thecontrol unit 98. The pressure in the conduit 100, representative of thetemperature in the enclosure 90, will be opposed in the control unit tosaid adjusted pressure, whereby there will be produced at the outlet ofsaid unit and impressed through the conduits 105 and 103 upon the motorelement of the valve 96 a pressure representing the difierence of saidopposed pres- A 7 sures. By suitable interrelation of elements, and byadjustments well known in the" art, but forming no part of the presentinvention, the performance of the valve 96 may be made such that itsadmission of temperatureefiecting agent to the enclosure 90 will be of asense and magnitude to tend to reduce to zero the difference between theopposed pressures applied to the control unit 98, and thus to maintainthe temperature in said enclosure at a value predetermined by thesetting of the regulator 97 through manual adjustment of the knob 33.

If the valve 106 be turned to the position shown in Figure 4, with thehandle 35 opposite Seal on the associated plate, the conduits 103, 104and 105 will become mutually isolated, and sealed. Thus, fluid in theconduit 103 will be trapped, so that the pressure applied to the motorelement of the valve 96 will remain constant, and the valve will rest inits established position. Pressure in the conduit 105 will continue tobe regulated by the control unit 98 but will be ineffective to produceany operative result. Pressure in the conduit 104 will continue subjectto adjustment by the regulator 97, and will be indicated by the spotter62 in the instrument 31, but will produce no effect on the operation ofthe system.

If the valve be turned to the position shown in Figure 5, designatedManual, the conduit 105 will remain cut off from the control valve andthe pressure in the conduit 1% will be directly applied through theconduit 103 to the motor element of the valve 96. Since said pressure isadjustable by setting of the regulator 97, the operation of the controlvalve 96 thus becomes directly subject to the knob 83, whereby theopening of said valve may be manually established at any desired value.

Attention may now be directed to details of the mechanical featurescharacterizing the mounting of the removable instrument 31 in theenclosing casing 32, and to the manner of its removal and replacement.Referring to Figures -19, inclusive, it will be seen that the mountingmembers 34, and 36 which extend through the base-plate 33 are providedwith short pipe or tubular projections 120, 121 and 122 respectively,interiorly communicating with said mounting members, and thus with theinteriors of the respectively attached fluid-pressureresponsiveelements. The tubular projections and 121 are extended a short distancetoward the front of the instrument near its center line, mad the tube122 is directly connected to the hollow plug member 116, which in turnis supported and maintained in alignment with the receptacle 109 bymeans of a mounting block 123 secured to the lower face of the plate 33at its rear extremity and toward one side thereof.

The tubular plug members 114 and 115 are each carried by a block member125 which in turn is secured to one extremity of a rod 126 slidablymounted in brackets 127 and 128 positioned on the lower surface of plate33. Also carried by the block member 125 are rearwardly projectingtubular members 130 and 131 internally communicating respectively withthe tubular plug members 114 and 115. Internal communication between thetubular member 130 and the tubular projection 120 is provided by meansof a looped element 132 formed of flexible tubing, such as Saran andcoupled at its extremities with said tubular member and projection.Similar connection is made between the tubular member 131 and thetubular projection 121 by means of a looped flexible element 135.

The rod 126 is, in the present instance, provided with a keywa asindicated, in which a pin rides to constrain the same against rotationabout its axis, whereby its displacement relative to its mounting isrendered solely longitudinal. Rod 126 may otherwise be constrainedagainst rotation as by being splined or formed of noncircularcross-section. A yieldable spring-latch 135 resiliently secured to theblock 111% and engaging a lip portion of the block 125 tends to maintainthe same mutually juxtaposed, so that as the plate 33' is subjected towithdrawal from the enclosing casing 32 alongthe rails 70- 71 thetubular plug members 1'14'and 115 for a portion of said withdrawal areretained in engagement with the receptacles 107 and 108 respectively,communication between the pressure-responsivemembers 37--38 and thecontrol piping being maintained through the looped flexible tubularelements 132 and 133 which, as indicated in the rcspective figures ofthe drawings, will be yieldably deformed with different relativepositions of the stationary and the movable parts of the combination.

Longitudinal excursion of the rod 126 relative to its supports islimited by a head portion 136 formed upon the forward extremity of saidrod, whereby upon withdrawal of the plate 33 beyond a predetermineddistance, as indicated in Figures 16 and 17, said head portion isengaged by the bracket 127, and the rod 126 and the block 125 carriedthereby forcibly displaced against the influence of the spring-latch135, withdrawing the tubular plugs 114 and 115 from their correspondingreceptacles and fully disconnecting the recording instrument from thecontrol piping, as indicated in Figures 17 and l9.

When the instrument assembly 31 is located in its normal operatingposition and fully inserted Within the case 32, and secured therein bymeans of the retaining screw 82-, the three tubular plug members 114,115 and 116 are in operative communication with their respectiveassociated receptacles, as indicated in Figure 15, and the latch member77, carried by the base-plate 33, occupies the position indicated inFigure 20, being constrained inwardly by engagement of the detentportion 78 with the unbroken side face of the rail 70, and exerting noholding action.

In order to withdraw the instrument assembly from the case, theretaining screw 82 is rotated to a position with its flat sideuppermost, as indicated in Figure 2, when it will clear the lug 81,leaving the instrument assembly free for longitudinal displacement. Asthe assembly is Withdrawn, the blocks 125 and 110 are maintained inmutual engagement by the spring-latch 135, and the brackets 127 and 1128slide freely along the rod 126. Displacement of the base-plate 33 withrespect to the rod 126 and block 125 is coordinated with thelongitudinal positioning of the detent 78 and the slot 76 in the rail'70 so that as the assembly is partially withdrawn, the latch 7'1 willassume the position indicated in Figure 14, the detent portion 78entering the slot and providing a positive restraint against furtherwithdrawal at the same time as the bracket 127, sliding along the rod126 approaches the head portion 136. Under this condition, the relativedisposition of cooperating elements beneath the plate 33 is as indicatedin Figure 16, the blocks 125 and 11 emaining. in cooperative engagementand pressure-fluid connections being maintained between the receptacles1 71d$ and the respectively associated pressure-rcsponsive members ofthe partially Withdrawn instrument assembly.

In the partially withdrawn position of the instrument assembly 31, asdetermined by the latch member I7 in its engagement with the slot 76,the indicating and recording instrumentalities, comprising the scale 50and cooperating pointers, the chart 51 and chart-drive, as well as therecording pen 60, are rendered readily accessible for inspection andservicing, while at the same time remaining operative to produce anindication and an uninterrupted record of the controlled variable, aswell as the indication of the control point. In the present instance,only two of the pressure-responsive elements, those representing thecontrolled variable and the set point, remain operative under thecondition of partial withdrawal of the instrument assembly, but asindicated in Figure 3, all the pressure-deflecting members may remainactive under such condition, and the same can be effected bymodification of the design of the cooperating plug and receptaclemembers; Since the mechanical connections between thehandle 85 and thevalve 106 and 9 between the knob 83 and the regulator 97 areincorporated within the stationary casing 32 and are in no way disturbedby withdrawal of the instrument assembly, it will be apparent that whilethe instrument isin this condition complete control is retained, withindication of the set point and both an indication and a record ofthemeasured and controlled variable.

Should it become desirable to effect complete withdrawal of theinstrument assembly 31 from the casing 32, the detent 73 is releasedfrom engagement with the slot 76 by manual depression of thefinger-piece 80, shown in Figures 1 and 16 as projecting through theedge por-,

tion 72 of the plate 33 slightly to the fornt of the enclosing casing32. The latch member thus disengages the slot 76 and assumes theposition indicated in Figure 22, releasing the instrument assembly forcomplete withdrawal from the case, as indicated in Figure 17. As saidassembly is withdrawn, the bracket 127 engages the head portion 136 ofthe rod 126, thereby overcoming the restraint of the spring-latch 135and withdrawing the block 125 and the plugs 114 and 115 from engagementwith the block 110 and the receptacles 107 and 1051 respectively,whereupon said receptacles exercise their selfsealing characteristic toclose the associated conduits against leakage to the atmosphere, and thespring-latch 135 reverts to the position indicated in Figure 19. At thesame time, the latch 77, passing the forward extremity of the rail 70,assumes the position shown in Figure 23.

As hereinbefore pointed out, removal of the complete instrument assembly31 from its enclosing case does not in any way interfere with theperformance of the control system. As this removal is effected, theself-sealing receptacles 107, 103 and 109 cut off escape of pressurefluid in the associated conduits 100, 103 and 104; and, While removal ofthe instrument eliminates from the system the normal means forquantitatively determining the regulated variable or the set point ofthe control, the apparatus will continue to operate as a blindcontroller performing all its regulatory functions in a normal manner. I

It is to be understood that while the present invention is especiallywell suited for use in and has been described in connection with apneumatically actuated system, many of its important advantages areattained when the invention is utilized with other types of apparatus.In particular, the electrically operated devices of an electrical systemmaybe mounted on base-plate 33 in casing 32 and corresponding electricalconnecting devices are then utilized in place of those shown.

In the operation of practically all automatic control installationsthere arise occasions where it becomes desirable that regulation of thevariable be rendered subject to the command of manually actuable means.This is especially true at times of starting up and of shutting down aprocess; but such occasions may develop at any time, and should be fullyprovided for in the installation. When transfer is made from automaticto manual, or from manual to automatic, control, it is of coursedesirable that such transfer should be as nearly as possible bumpless,i. e., that the main control valve should not be subjected to anyinfluence tending to cause it to make an abrupt change in its position.In a pneumatic control system, which has been selected as bestexemplifying the present invention, this bumpless characteristicrequires that as control is transferred from automatic to manual, orvice versa, the fluid pressures reaching the motor element of thecontrol valve under the respective conditions be mutually equal at theinstant of transfer. The peculiar adaptability of the present apparatusto the fulfillment of this condition will be apparent from aconsideration of the manner in which such transfers are effected.

It may first be assumed that the installation is performing normalcontrol under a substantially steady-state condition, with the three-wayvalve 106 in the position shown in Figure 3, this being indicated by thehandle pointing toward Automatic as in Figure 9 of the drawings. Thespotter 62 is set at a value of 5.4 on the lefthand graduations (whichmight, for example, represent a temperature of 540 degrees); and thepointer 61 in following the normal variations of automatic control isshown at a point slightly below the spotter. It may now be assumed thatit is desired to change from automatic to 7 manual control. Thethree-way valve 106 is first set to the Seal position, as shown inFigure 4 and as indicated in Figure 10. This cntraps the air in conduit103 at its last-regulated pressure as indicated by the index 63 on thescale 50. In order that there be no abrupt change in pressure as manualcontrol is introduced, it is essential that this pressurev be notsuddenly changed at that time. Thus, the pressure in the conduit 104should be the same as that in the conduit 103 before communicationbetween the same is established. To effect this condition, it isnecessary only to adjust the former of said pressures by manipulation ofthe regulator 97 through the control knob 83. As the position of thespotter 62 is representative of said pressure, there is thus provided ameans of comparing the two pressures prior to completing the transfer.By observing the position of the spotter 62, and, without regarding itsscale reading, adjustment of the pressure in the conduit 104 may beeffected until said spotter is in line'with the index 63, as indicatedin Figure 7, at which time the two pressures are matched, and thethree-way valve 106 may be turned to the Manual position, as shown inFigure 5 and as indicated in Figure 11, without any change in pressureapplied to the valve motor and without any bump in the control.

The degree of opening of the control valve 96 is now wholly subject tothe pressure in the intercommunicating conduits 103 and 104, asregulated by the setting of the control knob 83; and this may be variedat will, so long as the valve 106 remains set in the Manual posi-- tion.During such time the pointer 61 will continue to indicate, and the penor stylus 60 to record, the value of the controlled variable, while thespotter 62 and the index 63 will remain in coincident positionsindicating the pressure applied to the motor element of the controlvalve 96.

The procedure for effecting a transition from manual. to automaticcontrol is substantially the reverse of that set forth for introducingmanual control. The valve 106 is first set to the Seal position, asshown in Figure 4 and as indicated in Figure 12, thus entrapping air inthe motor element of the valve 96 and in the conduit 103 at a pressureas last established by the regulator 97.

Assuming a reasonably steady-state condition, this pressure will be suchas to cause the regulated variable to have a value as indicated by thepointer 61. By adjusting the regulator 97 until the spotter 62 assumes aposition in coincidence with said pointer, the air pressure in theconduit 104, balancing in the control unit 93 that in the conduit 100,will cause the pressure in the conduit 105 to attain a pressurecorresponding tothat in the conduit 103, whereupon the valve 106 may bethrown to the position shown in Figure 3 and as indicated in Figure 13without abrupt change of pressure in the motor element of the controlvalve 96, thus completing a bumpless reestablishment of automaticcontrol.

The terms and expressions which I have employed are used-as terms ofdescription and not of limitation, and I have no intention, .in the useof such terms and expressions, of excluding any equivalents of thefeatures shown and described or portions thereof, but recognize thatvarious modifications are possible within the scope of the inventionclaimed.

What is claimed is:

g 1. Controlling and indicating apparatus for controlling and indicatingthe magnitude of a variable condition, comprising a control valve orregulating the admission 'of a condition-affecting agent, afluid-operated motor element coupled to said control valve,condition-sensitive means and means actuated thereby for producing afirst fluid pressure representative of said magnitude, an adjustableregulator adapted to produce a second fluid pressure adjustable at will,pressure-sensitive control means responsive to said first and secondfluid pressures for producing at an outlet thereof a third fluidpressure representative of the difference between said first and secondpressures, a first conduit for carrying fluid at said first pressure andcoupled to the input side of said pressuresensitive control means, asecond conduit for carrying fluid at said second pressure and coupled tothe input side of said pressure-sensitive control means where said firstand second fluid pressures are opposed one to the other, a third conduitcommunicating with said outlet, a fourth conduit coupled to said motorelement, valve means for selectively coupling said fourth conduit witheither of said second and third conduits, a casing, support means,releasable means quick detachably securing said support means in saidcasing in a fully mounted position and for automatically securing saidsupport means in a predetermined partially withdrawn position relativesaid casing, exhibiting means on said support means and forindependently indicating the magnitudes of said first and second fluidpressures as well as the fluid pressure in said fourth conduit, couplingmeans for connecting said exhibiting means in energy transfer relationwith sources of said last mentioned respective fluid pressures andincluding quick disconnect means and yieldable connecting means on saidsupport means for maintaining said exhibiting means in operative and inenergy transfer relation with said sources of fluid pressure when saidsupport means is in its fully mounted position relative to said casingand when said support means is a least partially withdrawn therefrom.

2. In combination with indicating apparatus including exhibiting meansfor indicating values of a variable condition and actuating means in apanel member for connection with said exhibiting means in energytransfer relation; mounting means for releasably securing saidindicating apparatus in said panel member comprising guide meansdefining a predetermined path along which said indicating apparatus ismovable into and out of said panel member through an intermediatepartially withdrawn position, separable coupling means including oneportion mounted on said panel member and another portion releasablyconnected thereto, means movably connecting said another portion of saidseparable coupling means to said inidicating apparatus and adapted toallow limited movement of said another portion relative to saidindicating apparatus, yieldable means coupling said another portion ofsaid separable coupling means with said exhibiting means so that saidindicating apparatus is movable along said path from its insertedposition in said panel member to at least said partially withdrawnposition while said portions of said separable coupling means remainengaged and maintain said exhibiting means and said actuating means inenergy trasfer relation, and means for automatically decoupling saidseparable coupling means in response to Withdrawal of said indicatingapparatus beyond said partially withdrawn position while maintainingsaid yieldable means substantially free of strain incident to saiddecoupling.

3. In combination with indicating apparatus including energy translatingmeans for indicating values of a variable condition and a panel memberhaving actuating means for connection with said energy translating meansin energy transfer relation; mounting means for releasably securing saidindicating apparatus in said panel member comprising guide meansdefining a predetermined path along which said indicating apparatus ismovable into and out of said panel member through an intermediatepartially withdrawn position, quick releasable latch means forautomatically securing said indicating apparatus in said partiallyWithdrawn position, quick disconnect separable coupling means includingone portion mounted on said panel member and another portion on saidindicating apparatus, means movably connecting said another portion ofsaid separable coupling means to said indicating apparatus and adaptedto allow limited movement of said another portion relative to saidindicating apparatus, yieldable means coupling said another portion ofsaid separable coupling means with said energy translating means so thatsaid indicating apparatus is movable along said path from its insertedposition in said panel member to at least said partially withdrawnposition while said portions of said separable coupling means remainengaged and maintain said energy translating means and said actuatingmeans in energy transfer relation, and means for automaticallydecoupling said separable coupling means in response to withdrawal ofsaid indicating apparatus beyond said partially withdrawn position whilemaintaining said yieldable means substantially free of strain incidentto said decoupling.

4. In combination with indicating apparatus including exhibiting meansfor indicating values of a variable condition and actuating means in apanel member for connection with said exhibiting means in energytransfer relation; mounting means for releasably securing saidindicating apparatus in said panel member comprising guide meansdefining a predetermined path along which said indicatin" apparatus ismovable into and out of said panel member through an intermediatepartially withdrawn position, separable coupling means including oneportion mounted on said panel member and another portion releasablyconnected thereto, yieldable means coupling said another portion of saidseparable coupling means with said exhibiting means so that saidindicating apparatus is movable along said path from its insertedposition in said panel member to at least said partially withdrawnposition While said portions of said separable coupling means remainengaged and maintain said exhibiting means and said actuating means inenergy transfer relation, and means for automatically decoupling saidseparable coupling means in response to withdrawal of said indicatingapparatus beyond said partially withdrawn position while maintainingsaid yieldable means substantially free of strain incident to saiddecoupling.

5. A quick releasable mounting for indicating apparatus'havingexhibiting means as well as energy translating means adapted forconnection in energy transfer relation within a panel member withactuating means for the same, comprising support means, said exhibitingmeans and said energy translating means being supported by said supportmeans and operatively connected one with the other, guide means defininga predetermined path along which said support means is movable into andout of said panel member through an intermediate partially withdrawnposition in which at least said exhibiting means is accessible fromoutside said panel member, means for automatically releasably securingsaid support means in said partially Withdrawn position, means formaintaining said actuating means and said energy translating means inenergy transfer relation when said support means is withdrawn to atleast said partially Withdrawn position and including quick disconnectseparable coupling means having one portion thereof mounted on saidpanel member and another portion thereof releasably connected thereto,yieldable means coupling said another portion of said separable couplingmeans with said energy translating means, whereby said support meanswith the exhibiting and energy translating means supported thereby ismovable along said path from its inserted position in said panel memberto at least said partially Withdrawn position while said portions ofsaid separable coupling means remain engaged and maintain said actuatingmeans in energy transfer relation with said energy translating means,means for'automatically decoupling said separable coupling means inresponse to withdrawal of said support means beyond said partiallywithdrawn position while maintaining said yieldable means substantiallyfree of strain incident to said decoupling.

6. A quick releasable mounting for indicating apparatus havingexhibiting means as well as energy translating means adapted forconnection in energy transfer relation within a panel member withactuating means for the same, comprising support means, said exhibitingmeans and said energy translating means being supported by said supportmeans and operatively connected one with the other, guide means defininga predetermined path along which said support means is movable into andout of said panel member through an intermediate partially withdrawnposition in which at least said exhibiting means is accessible fromoutside said panel member, quick releasable latch means forautomatically securing said indicating apparatus in said partiallyWithdrawn position, means for maintaining said actuating means and saidenergy translating means in energy transfer relation when said supportmeans is withdrawn to at least said partially withdrawn position andincluding quick disconnect separable coupling means having one portionthereof mounted on said panel member in a predetermined positionrelative to said path and another portion thereof supported by andmovable relative to said support means, aligning means orienting saidanother portion of said separable coupling means relative to said pathand said predetermined position whereby said portions are aligned forengagement one with the other as said support means is inserted in saidpanel member, yieldable means coupling said another portion of saidseparable coupling means with said energy translating means whereby saidsupport means is movable along said path from its inserted position insaid panel member to at least said partially withdrawn position whilesaid portions of said separable coupling means remain engaged andmaintain said actuating means and said energy translating means inenergy transfer relation, and means for automatically decoupling saidseparable coupling means in response to withdrawal of said support meansbeyond said partially withdrawn position while maintaining saidyieldable means substantially free of strain incident to saiddecoupling.

'7. A quick releasable mounting for indicating apparatus havingexhibiting means as well as energy translating means adapted forconnection in energy transfer relation within a panel member withactuating means for the same, comprising support means, said exhibitingmeans and said energy translating means being supported by said supportmeans and operatively connected one with the other, guide means defininga predetermined path along which said support means is movable into andout of said panel member through an intermediate partially withdrawnposition in which at least said exhibiting means is accessible fromoutside said panel member, means for automatically releasably securingsaid support means in said partially withdrawn position, means formaintaining said-actuating means and said energy translating means inenergy transfer relation when said support means is withdrawn to atleast said partially withdrawn position and including quick disconnectseparable coupling means having members forming opposite sides thereofcoupled respectively with said actuating means and said energytranslating means, means movably sup porting one of said members andorienting the same relative to the other of said members, yieldablemeans coupling the movable one of said members with the respective meansassociated therewith, whereby said support means is movable along saidpath from its inserted position in said panel member to at least saidpartially withdrawn position while said members of said separablecoupling means remain engaged and maintain said actuating means and saidenergy translating means in energy transfer relation and said movablemember is automatically oriented with and couples with the other memberof said separable coupling means when said indicating apparatus isinserted into said panel member for connection in energy transferrelation, and means for automatically decoupling said separable couplingmeans in response to withdrawal of said support means beyond saidpartially withdrawn position while maintaining said yieldable meanssubstantially free of strain incident to said decoupling.

8. A quick releasable mounting for indicating apparatus havingexhibiting means as well as energy translating means adapted forconnection in energy transfer relation within a panel member withactuating means for the same, comprising support means, said exhibitingmeans and said energy translating means being supported by said supportmeans and operatively connected one with the other, guide means defininga predetermined path along which said support means is movable into andout of said panel member through an intermediate partially withdrawnposition in which at least said exhibiting means is accessible fromoutside said panel member, means for maintaining said actuating meansand said energy translating means in energy transfer relation when saidsupport means is withdrawn to at least said partially withdrawn positionand including quick disconnect separable coupling means having membersform'- ing opposite sides thereof coupled respectively with saidactuating means and said energy translating means, means movablysupporting one of said members and orienting the same relative to theother of said members, yieldable means coupling the movable one of saidmembers with the respective means associated therewith, quick releasablelatch means for automatically securing said support means in saidpartially withdrawn position, and means for automatically decouplingsaid separable coupling means in response to withdrawal of said supportmeans beyond said partially withdrawn position while maintaining saidyieldable means substantially free of strain incident to saiddecoupling.

, 9. A quick releasable mounting for indicating apparatus havingexhibiting means as well as energy translating means adapted forconnection in energy transfer relation within a panel member withactuating means for the same, comprising a plate-like support member,said exhibiting means being supported on said plate-like member adjacentto one end thereof,'said energy translating means being supported onsaid plate-like member adjacent to the opposite end thereof, meansoperatively linking said exhibiting means and said energy translatingmeans, mounting means including a pair of elongated guide railssupported in said panel member in spaced parallel relation and defininga predetermined path, said platelike member having opposite sideportions thereof disposed for-sliding engagement with said guide railswhereby said plate-like member may be inserted into and withdrawn fromsaid panel member through an opening formed therein along said path withsaid plate-like member passing through an intermediate partiallywithdrawn position, latch means for quick releasablylocking saidplate-like member in said partially withdrawn position in which at leastsaid exhibiting means is accessible from outside said panel member,mating quick disconnect coupling members one mounted on said panelmember and coupled to said actuating means, means for automaticallysealing .said one coupling member when the other coupling member isremoved from mating engagement therewith, an elongated rod slidablymounted and movable between two extreme positions on said plate-likemember and having one end thereof presented toward said opposite end ofsaid plate-like member, said rod being connected to and movablysupporting the other of said coupling members adjacent to said oppositeend of said plate-like member, means for orienting said other couplingmember with said one coupling member, yieldable means coupling saidother coupling member with said energy translating means, whereby saidplate-like memseats? her is movable along said path from its insertedposition in said panel member to at least said partially withdrawnposition while said coupling members remain engaged and maintain saidactuating means and said energy translating means in energy transferrelation, and means for automatically disengaging said coupling membersone from the other and operative when said latch means is released andsaid plate-like member withdrawn from said panel member.

10. A quick releasable mounting for indicating apparatus havingexhibiting means as well as energy translating means adapted forconnection in energy transfer relation within a panel member withfluid-pressure-actuating means for the same, comprisinga plate-likesupport member, said exhibiting means being supported on said plate-likemember adjacent to one end thereof, said energy translating means beingsupported on said platelike member adjacent to the opposite end thereof,means operatively linking said exhibiting means and said energytranslating means, mounting means including a pair of elongated guiderails supported in said panel member in spaced parallel relation anddefining a predetermined path, said plate-like member having oppositeside portions thereof disposed for sliding engagement with said guiderails whereby said plate-like member may be inserted into and withdrawnfrom said panel member through an opening formed therein along said pathwith said plate-like member passing through an intermediate partiallywithdrawn position, latch means for quick releasably locking saidplate-like member in said partially withdrawn position in which at leastsaid exhibiting means is accessible from outside said panel member,mating quick disconnect fluid coupling members one mounted on said panelmember and coupled to said actuating means, means for automaticallysealing said one coupling member when the other coupling member isremoved from mating engagement therewith, an elongated rod slidablymounted for movement between two extreme positions on said plate-likemember and having one end thereof presented toward said opposite end ofsaid plate-like member, said rod being connected to and movablysupporting the other of said coupling members adjacent to said oppositeend of said plate-like member, means for orienting said other couplingmember with said one coupling member, flexible fluid conduits fortransmitting fluid pressure from said actuating means to said energytranslating means and connected to said other coupling member and tosaid energy translating means, whereby said plate-like member is movablealong said path from its inserted position in said panel member to atleast said partially withdrawn position while said coupling membersremain engaged and maintain said actuating means and said energytranslating means in energy transfer relation, and means on said rod andsaid plate-like member for automatically disengaging said couplingmembers one from the other and operative when said latch means isreleased and said plate-like member Withdrawn from said panel member.

11. A quick releasable mounting for indicating apparatus havinexhibiting means as well as energy translating means adapted forconnection in energy transfer relation within a panel member withfluidpressure-actuating means for the same, comprising a plate-likesupport member, said exhibiting means being supported on said plate likemember adjacent to one end thereof, said energy translating means beingsupported on said plate-like member adjacent to the opposite endthereof, means operatively linking said exhibiting means and said energytranslating means, mounting means including a pair of elongated guiderails supported in said panel member in spaced parallel relation anddefining a predetermined path, said plate-like member having oppositeside portions thereof disposed for sliding engagement with said guiderails whereby said plate-like member may be inably mounted for movementbetween two extreme positions on said plate-like member and having oneend thereof presented toward said opposite end of said platelike member,said rod. being connected to and movably supporting the other of saidcoupling members adjacent to said opposite end of said plate-likemember, means for orienting said other coupling member with said onecoupling member, flexible fluid conduits for transmitting fluid pressurefrom said actuating means to said energy translating means and connectedto said other coupling member and to said energy translating means, saidfluidpressure-actuating means including a three-position valve forselectively setting said actuating means for either automatic or manualadjustment and operative when said plate-like member is in saidpartially withdrawn position as well as when said plate-like member isin its fully inserted position, whereby said plate-like member ismovable along said path from its inserted position in said panel memberto at least said partially withdrawn position while said couplingmembers remain engaged and maintain said actuating means and said energytranslating means in energy transfer relation, and means on said rod andsaid plate-like member for automatically disengaging said couplingmembers one from the other and oper-ative when said latch means isreleased and said platelike member withdrawn from said panel member.

12. In a pressure-fiuid-actuated apparatus for controlling the magnitudeof a variable condition and of the type comprising a control valve forregulating the admission of a condition-affecting agent and having afluid-operated motor element, condition-sensitive means and meansactuated thereby for producing a first fluid pressure representative ofsaid magnitude, an adjustable regulator adapted to produce a secondfinid pressure adjustable at will, a control device sensitive to saidfirst and second fluid pressures and having a fluid outlet andresponsive to the difference of said pressures to produce at said outleta third fluid pressure representative of said difference, a firstconduit adapted to carry fluid at said first pressure and to admitthesame to said control device, a second conduit adapted to carry fluidat said second pressure and to admit the same to said control device tobe pressure-wise opposed to said first fluid, a third conduitcommunicating with the outlet of said device, and a fourth conduitadapted to apply pressure fluid to the motor element of said controlvalve to operate the same, a three-position valve connected to saidsecond, third and fourth conduits and having a first position providingcommunication between said third and fourth conduits, a second positionwherein said second, third and fourth conduits are mutually isolated anda third position providing communication between said second and fourthconduits, individual pressure-responsive deflectable elementsconnectedto said first, second and fourth conduits respectively and havingdiscrete exhibiting members deflectable in proportion to the respectivepressures therein, said exhibiting members in their excursions followingsubstantially a common path whereby at any portion of said path theirdeflected positionsmay be compared and matched.

13. In a pressure-fiuid-actuated apparatus for controlling the magnitudeof 'a variable condition having a control valve with a fluid-operatedmotor element for regulating the admission of a condition-affectingagent, condition-sensitive means and means actuated thereby forproducing a first fluid pressure representative of said magnitude, anadjustable regulator adapted to produce a second fluid pressureadjustable at will, a control device sensitive to said first and secondfluid pressures and having a fluid outlet and responsive to thedifference of said pressures to produce at said outlet a third fluidpressure representative of said difference, a first fluid conduit forcarrying fluid at said first pressure and connected between said secondmentioned means and the inlet side of said control device, a secondfluid conduit for carrying fluid at said second pressure and connectedbetween said adjustable regulator and the inlet side of said controldevice wherein said second fluid pressure is pressure-wise opposed tosaid first fluid pressure, a third fluid conduit communicating at oneend thereof with the outlet of said control device, a fourth conduitconnected to the motor element of said control valve for applying fluidunder pressure thereto for operating the same, a three-position valvecoupled to said second, third and fourth conduits and having a firstposition providing communication between said third and fourth conduitswhile isolating the second conduit therefrom, a second position whereinsaid second, third and fourth conduits are mutually isolated and a thirdposition providing communication between said second and fourth conduitswhile isolating said third conduit therefrom, pressure-responsive energytranslating means coupled to each of said first, second and fourthconduits, a plurality of defiectable elements one for each of saidfirst, second and fourth conduits connected to said energy translatingmeans and each. defiectable thereby in proportion to the pressure in therespective conduits, said defiectable elements being mounted to sweepclosely adjacent paths, the defiectable element associated with saidsecond conduit being alignable with either of the remaining defiectableelements so that said second pressure may be matched with either saidfirst pressure or the pressure in said fourth conduit while saidthree-position valve is in said second position in accordance withwhether the apparatus is being switched to automatic or manualoperation.

14. In a pressure-fluid-actuated apparatus for controlling the magnitudeof a variable condition and having a control valve with a fluid-operatedmotor element for regulating the admission of a condition-affectingagent, condition-sensitive means and means actuated thereby forproducing a first fluid pressure representative of said magnitude, anadjustable regulatory means for producing a second fluid pressureadjustable at will, control means sensitive to said first and secondfluid pressures and responsive to the difference of said pressures toproduce a third fluid pressure, means for selectively coupling saidsecond or third fluid pressure with the motor element of said controlvalve and including a three-position valve, said three-position valvehaving a first position coupling said control means to said motorelement, a second position isolating said motor element and a thirdposition coupling said regulatory means to said motor element, and aplurality of individual pressure-responsive defiectable means connectedrespectively to sources of said first and second fluid pressures and tothe input side of said motor element, said defiectable means eachincluding an exhibiting member and for providing a comparison of thefirst and second fluid pressures and the pressure on the input side ofsaid motor element, whereby said second fluid pressure may be readilyadjusted to correspond with either said first fluid pressure or thefluid pressure on the input side of said motor element when saidthree-position valve is in its second position in accordance withwhether the apparatus is being switched to automatic or manualoperation.

References Cited in the file of this patent UNITED STATES PATENTS2,129,723 Wood Sept. 13, 1938 2,202,485 Fitch May 28, 1940 2,302,707Mejean Nov. 24, 1942 2,333,834 Vetter Nov. 9, 1943 2,369,887 EckrnanFeb. 20, 1945 2,438,371 Marholz Mar. 23, 1948 2,486,764 Singer Nov. 1,1949 2,528,735 Bristol Nov. 7, 1950 OTHER REFERENCES Bulletin, 2M48Hagan Building, Pittsburgh, Pa., pp. 2 and 3 relied on.

